I have a concern about HP3000 security,

How hard would it be to launch a virtually undetectable unauthorized attack
on an HP3000 while hiding behind a large private global network? This is
assuming that you don't have a login or password for the HP3000. Isn't it
true that the HP3000 is a production machine and that it is most likely not
even connected to the Internet? And if it were to be connected wouldn't it
be behind a firewall? I have also heard that the HP3000 has logs which would
give away the identity of the intruder.

Thank you for your answers,